Spline lubricants for BMW Airheads motorcycles
Airheads need scheduled lubrication on transmission input shaft splines (never grease the clutch disc splines themselves); and, rear wheel cup splines and associated rear drive output splines on the twin-rear-shock models.
Numerous lubricants have been tried in many different climatic and riding conditions, over many years. Some newer lubricants are still being tested. There does not seem to be any magic, perfect lubricant for these places. BMW has specified quite a few lubricants over the years, such as Staburags, Optimoly, ETC. The author has never believed these lubricants were as good as some others, at the times BMW had those recommendations. The author, and others, have done long-term testing on various lubricants. This article you are reading no longer lists these lubricants, nor recommended lubricants, as the latest information will be found HERE:
https://bmwmotorcycletech.info/chemicalsetc.htm where the author keeps the information up-to-date. The spline lubricant information is at item #6A in that article.
Later model (exact year and models are unclear, probably late 1980’s) transmission input splines are SUPPOSEDLY nickel-plated and do not require cleaning and relubrication quite as often, but 30,000 miles seems the practical LIMIT, and for earlier ones perhaps 20,000 is the limit. Best you do it before these mileages, at least once, and then, upon inspection, adjust the interval for the next clean/lube, assuming the same lubricant. Once a spline shows rusting, you are LOSING METAL! The transmission input splines are fine-pitch and not very deep….you do NOT want them to fail!
Do NOT lubricate clutch disc splines; rather, first clean and then lubricate the transmission input shaft splines. Do NOT spray cleaner into the DISC splines, as doing so can put an oily/greasy mess into the friction disc. By NOT lubricating the disc splines, you AVOID moving grease into the clutch disc during reassembly of transmission input shaft into the clutch disc. Work the grease into the input shaft splines. While the perfect job is done by transmission removal for extensive cleaning of the area, if the transmission is moved backwards an inch or more, you can do a decent job with common acid brushes (shorten the bristles by about half of normal length to make them stiffer). Use tape (OR?) to fasten the acid brush to a wood dowel for lengthening the brush tool. Make two…one for cleaning with a solvent, one for applying the grease.
Since the transmission will be removed, or at least moved backwards, I suggest you check the throwout bearing and lubricate the clutch arm; some later arms have needle bearings…you may have to soak the arm in such as kerosene to clean them. Do not use moly grease in a clutch arm needle bearing.
Information on those subjects, including hints on avoiding the dreaded broken transmission clutch ears, throwout bearing, plus more extensive information on just how to go about the various splines lubrication, is the following article numbers on the Author’s website:
1. Article number 43
2. Article number 60, sub-section 9
For the rear wheel cup splines and the associated rear drive output splines, I suggest cleaning and greasing at each rear tire change. Clean the DRIVE’S splines (that means the rear drive male splines) with a medium stiff brush, moving the brush from the seal towards the left. I use an old toothbrush. DO NOT USE HARSH SOLVENTS, WHICH CAN INJURE THE SEAL. YOU PROBABLY WILL NOT NEED A SOLVENT AT ALL. Do not leave a bristle in the seal. DO NOT brush TOWARDS the rear drive seal! Leave only a light amount of grease in the rear drive output splines. You can use plenty in the WHEEL CUP splines, just clean the cup as best you can with what you have, such as deep brushes, smoking pipe cleaners, whatever, and then use a tiny screwdriver (OR?) to put plenty of grease into/onto the WHEEL CUP SPLINES. Cleaning the wheel cup before re-greasing is a chore; but it need not be 100% perfect.
NOTE 1: Paralever Airheads have splines at the aft end of the driveshaft. These splines couple to the rear drive. The Paralever driveshaft housing does NOT contain an oil bath like the other models do. Lubrication should be done now and then at the Paralever rear splines (check the input too).
NOTE 2: Whenever a rear drive is removed ON ANY MODEL OF AIRHEAD the rear drive unit’s input nut needs to be checked for tightness. That is tricky, as the wheel wants to move, and hints are in the author’s website. DO NOT allow that input nut to get loose!
https://bmwmotorcycletech.info/index.html
Originally published in 2004, this article has been revised several times since. The present revision is that of 20 February 2021, when the changes were minor (emphasis on some items) plus http>https.
Copyright 2021, R. Fleischer
